You may have heard it said that there are two equally acceptable ways to install a new roof: 1) overlaying the old roof with new shingles (also known as a layover) and 2) completely removing the old roof and then installing the new (commonly referred to as a tear off). We’re sorry to have to report that this is simply not true. While some contractors continue to try to propagate the false equivalency of these methods, the fact is a tear off is always the better, safer option since there are just too many dangerous risks when it comes to doing a layover. Don’t believe us? Maybe these eight problems with roof layovers will convince you:
1. No Decking Inspection
Installing new shingles over old shingles provides no opportunity for inspecting the decking. Only by completely removing the old roofing system can a contractor give a roof’s decking the proper check up it needs. The plywood boards that make up the backbone of your roof could be rotting away up there, but you won’t know that until it’s too late if you let your contractor get away with overlaying your old faulty roof with a new one.
2. Neglecting the Secondary Layers of Protection
One of the great things about a tear off is it allows your contractor to give your roof the full secondary leak protection it needs. Layovers, on the other hand, prohibit some necessary steps from occurring. For instance, you can’t install ice and water shield over old shingles because it needs to adhere to clean plywood decking boards to seal correctly. Without ice and water shield, water from wind-blown rain and ice dams can easily sneak below the top layer of shingles and wreak all sorts of havoc on the old roof underneath.
There may also be problems with your roof’s flashing that you are unaware of and will remain unaware of if you settle for a layover. Sometimes the process of overlaying shingles can even damage the flashing beneath the old layer because roofers can’t see it to avoid stepping on and denting it. Flashing is essential for protecting the most vulnerable areas of your roof, and a getting a new roof is the perfect time to inspect those areas and upgrade your flashing. Don’t rob yourself of that significant benefit by accepting a purely cosmetic layover.
3. Weight Hazards
Let’s get one thing straight: shingles are heavy. For every 100 square feet of roof, one layer typically weighs somewhere between 200-350 lbs depending on the type of shingles. Add another layer on top of that, and you’re talking about around 500 lbs of weight bearing down on every 100 square feet of your roof decking. Most roofs were only built to handle a certain amount of weight and will likely collapse if they exceed their limit. Rotten or damaged decking will only add to the risk of your roof caving in; however, as we established above, there’s no way of knowing the state of your decking if you get a layover. So you’d be gambling that your roof is in good enough shape to handle the extra weight, which is a dangerous risk to take.
4. Worsening Underlying Issues
If the reason you’re getting a new roof is that your old roof isn’t doing its job anymore, then why would you leave that lazy dying roof on your home? Putting new shingles over it isn’t going to help keep it alive. In fact, doing so could expedite your old roof’s deterioration because damaging heat and moisture may get trapped between the layers and eat away at the old roof. In this case, it won’t take long before you begin to regret covering up your problems instead of tearing them out and starting from scratch.
5. Lower Life Expectancy
While the shingles you choose for your roof may have an impressive fifty-year life expectancy, they won’t last nearly that long if you lay them over shingles that have already had years of exposure to the elements. Those old shingles will only detract from the lifespan of the shingles above them, making it more likely that you’ll have to be getting both layers replaced sooner than you would have liked.
6. Warranty Woes
A shingle manufacturer’s warranty covers shingle defects, not craftsmanship errors, and a layover is a major craftsmanship error. The problems that result from a layover often have to do more with the old shingles underneath than the new shingles on top. Shingle manufacturers understand this and want to protect themselves from having to take responsibility for an issue their product didn’t cause. So don’t expect to receive much warranty coverage for your roof if you take some beautiful new shingles and slap them on your old weathered roof.
7. Uneven Shingle Surface
It’s a lot tougher to get shingles to lay flat like they are supposed to when installing them over other shingles. Slight imperfections in the lower layer often manifest themselves as dips and bulges in the upper row. For this reason, rainwater won’t flow as smoothly off of a roof with multiple layers as it would if it had a single layer installed flat across the decking. The water may even begin to pool on your roof, which is never a good thing as it can lead to mold and mildew growth as well as other costly roof problems.
8. Costlier and Messier Later On
So why do people accept layovers? Most folks view them as cheaper, less messy, and less time-consuming than tear offs; and while they are all of those things during initial installation, replacing multi-layer roofs is a much different story.
The fact is you can’t just keep adding another layer of shingles when your current layer outlives its effectiveness. Most cities around the country legally prohibit three or more layers from being installed on a roof, making a tear off eventually necessary. And once it comes time to remove all of those layers, you’re not going to like the massive bill or the extra debris that comes with it. Take it from us. Removing multiple layers of shingles is a long and messy task, which is why contractors charge more for each layer they have to remove and why you don’t want anything to do with it.